Fluid sprinkling – spraying – and diffusing – Electrostatic type – With electrogasdynamic generator in spray device
Patent
1987-09-11
1989-01-17
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Electrostatic type
With electrogasdynamic generator in spray device
239698, 239705, 239706, 2395905, B05B 502
Patent
active
047983400
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to an electrostatic powder-spraying device with triboelectric powder charging by means of a powder pipe surrounding a delivery channel for the spray powder and of at least one displacement body located in the flow channel in order to boost the flow velocity, whereby the powder pipe is grounded on the outside and provided at least on its inside with a triboelectric material, which is arranged in the elctrostatic contact series at a distance from the material of the powder particles to be sprayed.
A comparable device for powder spraying is known from the German published specification No. 29 38 806. Therein the charging of the powder is done in a pipe-shaped nozzle element, whose flow channel is narrowed by a guide body, in order to increase the velocity and to produce a vortex. In addition, the outside of the nozzle is grounded or connected to high tension. Thereby the particles with opposite charges can be separated at a contact with the walling of the nozzle which is coated with a triboelectric material or displacement body. Reportedly the charging of the particles is improved through this device.
However, a separate electric field has to be introduced between the nozzle and the work piece to guide the charged particles towards the material. Since the electrostatic field varies with the points, edges and other protrusions of the workpiece, neutral zones are created on the workpiece. The coating powder can by this apparatus only to an insufficient extent reach the edges and crevices in the workpiece. As a result, the coating is uneven, which is the basic cause of early surface damage such as rust spots or the like, to the coated workpiece.
The invention departs from the electrostatic device for powder spraying as described above and aims towards the object of building such a device in the simplest manner. Deposition of the coating powder should be uniformly even in the case of workpieces with complicated configurations and the efficiency of this deposition should be increased.
SUMMARY OF THE INVENTION
In order to solve this problem according to the invention an additional charging device for the triboelectrically charged powder particles is used, with the same polarity as the one induced during the electrostatic charging.
This way, the charge of the powder particles can be increased so much that these particles can find their way to the workpiece, without introducing an electrostatic field between the spraying device and the workpiece and, to a large extent, without depending on other guiding forces, such as gas pressure-flow forces and the like. Due to this, the powder particles can reach into complicated recesses in the workpiece, the coating is improved over the entire surface, and protection is increased against damage or destruction from the outside.
It is therefore essential that the electrostatic charging through the selection of the appropriate triboelectric material and of the spraying powder, as well as through the guiding of the powder flow to the fixed walling of the device be performed as intensively as possible, respectively with the required flow velocity and to see to it that the charge which is created on the device side is lead away.
The aftercharging has to be performed primarily through an electrode supplied by an electric high-voltage power line, as radially inwardly extending wire electrodes. However, it can also be appropriate to perform a further aftercharging immediately before the exit of the powder from the nozzle, which under certain circumstances can again be performed triboelectrically.
Particular importance is attached to the configuration and arrangement of multiply provided displacement bodies, which can be located in the flow channel, but also in a preceding transport channel, and finally shortly before the nozzle exit.
BRIEF DESCRIPTION OF THE DRAWING
Further features and advantages of the invention are described in more detail through the following description of embodiment examples of the
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Pfeifer Kurt
Vohringer Gerhard F.
Dubno Herbert
ESB Elektrostatische Spruh- und Beschichtungsanlagen G.F. Vohrin
Jones Mary Beth O.
Kashnikow Andres
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